Ok.....lets understand that there is a big problem with copper radiators and ali components on engines there is a lot on the Internet about this and its a real problem like we saw on Dirks car it went for 420 od 000 km and coused a problem in 3500 odd km .
When Michael had it in for some tlc we did some tests and found about 4 v between engine and radiator when ignition was on . With ignition off we got about 0.9 to 1v difference between motor and radiator .
What we have to realise is that there are 2 tipes of problems here .....galvanic corrosion ....and the battery effect.but you guys can go read all about it there are a lot of info on the webb
We managed to stop the galvanic corrosion by connecting the radiator the motor with a copper wire . The battery effect was below 0.2v afer we replaced the antifreeze with nissan ones i think it was 4l as per nissan spec.
What Michael did was where the thermostat double acting part was serpose to seat it ate away a round little place that was just about the size of my pinkie . As from wat we could dig up on the web it eats the place where the base metal (ali) is the cleanest....as soon as the galvanic corrosion kicks in it contaminate the coolant with in turn makes the coolant more conductive and so the problem gets worse and worse.we didn't take any pics but the housing was perfect only where the alli was shiny with slight black marks on the sides .
By stopping the galvanic and keeping the coolant non conductive a person can limit the effect to a minimum
This mod stops the problem of the double acting thermostat not sealing and forces all the water to flow via radiator. Also now there is a big blob of clean ali where the hole used to be and this now works as a sacrifical annode between cooling fluid changes

We ,me and Michael have played with several 4.2 diesel patrols and have come to the conclusion that alli radiators are the way forward.
After we fitted the madman we could see that once the egt goes over 400 the water temperature rises up ....the only way to get it down is to get egt below say 350 and the water temp wil drop to below 95 again ...
Gustav 4.2td can sit at 140 all the time and not go over 95 deg . Water temp . Attie with his bakkie after Michael made it goes says he can sit at 160 for long periods no problems
Even oom Macs 4.2 battles to get hot .
On Andre GQ we did the same mod and he had like 6v between the engine and radiator .
Iam sending my alli radiator in to change the top tank so that i can use a pressure cap. Michael is waiting for delivery of his alli one so we will keep you posted on the findings
Dave Jones is bringing his 4.2 for some tlc today we will have to see what the story is there with his patrol

Will l change my 4.8 for my 4.2 diesel.....no i have the best of both worlds .....everyday having fun with my bakkie and weekend holidays with 4.8....
I hope it helps some of the forum guys to understand the problems with different tipes of coolers .....there is probably a reason why nissan decided to use alli coolers in the first place .....i also read that once you cover the copper with paint it is not such a good conductor anymore

I called the dealer, he said it's in excellent condition - a Zim vehicle that only did about 10000 km in last 10 years - apparently cos of registration paperwork issues. Those issues haven't gone away and they're still battling to register it (allegedly).

He said the vehicle is at his client's - near Edenvale, if anyone wants to have a look